The method of nitrogen balance was used to study the biological value (BV) of beef, rice and their combinations in growing male Wistar rats. To evaluate the quality of food proteins new parameters were used: potential biological value (BVp) and compensation coefficient (C). Group I-III rats were fed with boiled beef protein (the protein content was 5, 10 and 30%, respectively), group IV rats received 5% of rice protein, group V--20% of uncooked beef protein, group VI--a combination of rice and beef (1:2), group VII was also given a combination of rice and beef protein (1:1). The highest values of PER (gain in weight per 1 g of protein received), BVe (BV calculated experimentally) and NPU (natural protein utilization) were recorded in rats that received from 5 to 10% of beef protein. BVe of beef proved to be equal to BVp, and C was close to nul. A combination of rice and beef proteins in the ratio 1:1 had BVe equal to BVp of beef protein. The possibility of a new approach to the estimation of food protein quality has been proved.